Obojica moraju surađivati.

Obojica means both (of them), but specifically for two male people or a mixed pair treated in the masculine personal form.

So in this sentence, obojica refers to both men / both of them.

Related forms:

• obojica = both, for two males
• obje / obe = both, for feminine or neuter contexts depending on structure
• oboje = both, often used for a mixed pair, two children, or more generally the two of them

Learners often notice that Croatian has different forms for both, depending on who is being talked about.

Because obojica is grammatically treated as plural: both of them.

So the verb must also be in the 3rd person plural:

• mora = he/she/it must
• moraju = they must

Since obojica means both of them, Croatian uses:

• Obojica moraju ... = Both of them must ...

Yes. Obojica is the subject.

The structure is:

• Obojica = subject (both of them)
• moraju = finite verb (must)
• surađivati = infinitive (to cooperate)

So the whole sentence literally works like: Both of them must cooperate.

Because after morati (to have to / must), Croatian normally uses an infinitive.

So:

• moraju surađivati = must cooperate

This is very similar to English:

• They must cooperate

More examples:

• Moram ići. = I must go.
• Moramo učiti. = We must study.
• Moraju čekati. = They must wait.

Surađivati is an imperfective verb, meaning it focuses on an ongoing process, repeated action, or general activity.

It means to cooperate / to collaborate.

In a sentence like this, imperfective is natural because it refers to the general action of cooperating, not a single completed act.

A related noun is:

• suradnja = cooperation

Depending on region, you may also see spelling based on pronunciation traditions and standard preferences, but surađivati is a standard form.

Yes, often you could, but the nuance changes slightly.

• Obojica moraju surađivati.
  = Both of them must cooperate, specifically referring to two males.

• Oboje moraju surađivati.
  = Both of them must cooperate, but this is more natural for:

  • a mixed pair
  • two children
  • sometimes a more general the two of them

So if you know the two people are both male, obojica is the most precise form.

No. For two women, obojica is not correct.

For two women, you would use a feminine form such as:

• Obje moraju surađivati. = Both of them must cooperate.

So:

• obojica = both males
• obje = both females
• oboje = mixed pair / two children / general “both”

Here obojica is in the nominative, because it is the subject of the sentence.

You do not need to memorize all forms right away, but it helps to know that obojica changes by case, just like many Croatian pronouns and numerals.

In this sentence, the nominative is used because both of them are the ones performing or being required to perform the action.

No, Croatian word order is fairly flexible.

The neutral, straightforward version is:

• Obojica moraju surađivati.

But you may also hear:

• Moraju obojica surađivati.
• Surađivati moraju obojica.

These alternatives can shift emphasis:

• Obojica moraju surađivati. = neutral
• Moraju obojica surađivati. = emphasis on both
• Surađivati moraju obojica. = emphasis on cooperate

For learners, the original sentence is the safest and most natural basic order.

A rough pronunciation guide for an English speaker is:

• obojica ≈ oh-BOH-yee-tsa
• moraju ≈ MOH-rah-yoo
• surađivati ≈ soo-RAH-jyee-vah-tee

A few helpful notes:

• j is pronounced like English y
• c is pronounced like ts
• đ sounds roughly like a soft j/dj sound

So the whole sentence sounds approximately like:

oh-BOH-yee-tsa MOH-rah-yoo soo-RAH-jyee-vah-tee

Both are possible, depending on context.

• moraju can mean must
• it can also mean have to

So this sentence could be understood as:

• Both of them must cooperate
• Both of them have to cooperate

In many everyday contexts, Croatian morati covers both ideas.

Usually morati expresses necessity or obligation, but the exact nuance depends on context.

For example, it could mean:

• someone is requiring them to cooperate
• the situation makes cooperation necessary
• cooperation is the only practical option

So Obojica moraju surađivati does not by itself tell you why they must cooperate. It only states that cooperation is necessary or required.

Yes. Croatian often drops subjects when they are clear from context.

• Moraju surađivati. = They must cooperate.

But adding obojica makes it explicit that it is both of them, and can also add emphasis:

• not just one of them
• specifically the two men in question

So:

• Moraju surađivati. = they must cooperate
• Obojica moraju surađivati. = both of them must cooperate